Carbon coatings or films are known to be quite hard, chemically inert, corrosion resistant, and repellent to water vapor and oxygen. Such coatings are beneficial for their mechanical and chemical protective properties. Carbon thin films or coatings can be deposited on planar substrates in the form of, for example, graphite, crystalline diamond, and amorphous diamond-like networks (DLN). These films have differing physical and chemical properties.
DLN coatings have been applied to a wide variety of planar substrates, such as organic materials, polymeric films, ceramic substrates (e.g., aluminum oxide, barium titanate, and boron nitride), semiconductor substrates (such as silicon, germanium, gallium arsenide, cadmium telluride, and the like), and metal substrates (e.g., aluminum, stainless steel, nickel, and copper). Specific applications include magnetic rigid disks, sunglasses, ophthalmic lenses and infrared windows.
A number of methods have been developed for depositing carbon coatings on planar substrates, using solid carbon and hydrocarbon sources. Techniques using solid carbon sources include methods such as sputtering, laser evaporation, pulsed discharge rail gun, and cathodic arc deposition.
Several methods also exist to deposit types of organic or inorganic thin films onto particles. These include wet chemical methods, powder transfer onto particles in a mechanically or magnetically agitated particle bed, and fluidized bed chemical vapor deposition. None of these methods is useful for the deposition of densely packed diamond-like networks onto particles.